Information Processing in Agriculture (Dec 2023)
Peanut drying: Effects of various drying methods on drying kinetic models, physicochemical properties, germination characteristics, and microstructure
Abstract
The current work aims to explore the suitable drying technique for peanut pods which can be used for seeds or edible peanuts. Four drying methods, namely naturally-open sun drying as the control check (CK), hot air drying (HAD), pulsed vacuum drying (PVD), and radio frequency combined hot air drying (RF-HAD), were employed to dry peanut pods, and their effects on the nutritional quality attributes in terms of protein, fat, fatty acid contents, etc., germination characteristics, microstructure, color, texture, acid value and peroxide value of peanuts were explored. Mathematical models of peanuts drying with four drying methods were also established. According to the statistical parameters including the determination coefficient (R2)、root mean square error (RMSE) and chi-square value (χ2), the Weibull model was best for predicting the moisture ratio change kinetics of peanuts during its four drying processes. There were significant differences in physicochemical indexes of peanut by different drying methods (p < 0.05). Fat and oleic acid contents under RF-HAD were significantly higher than those by the other three drying methods. Compared with the naturally-open sun drying, RF–HAD reduced drying time by 76.70% and the microstructure of RF-HAD peanuts produced larger and more cavities. The RF-HAD kept better comprehensive nutritional quality, but the germination rate was reduced by 27.80%. PVD could maintain good nutritional quality and germination rate among these mechanical drying technologies. However, PVD had a longer drying time of 9.5 h than RF-HAD and HAD, and the microstructure of pulsed vacuum dried peanuts showed dense structure and less cavity. Hot air-dried peanut kernel held the highest protein (28.75%), fatty acids contents (26.11%) and germination rate (88.00%). However, peanut kernel dried by HAD showed poor qualities, such as high acid value, peroxide value and large color changes. These findings indicated RF-HAD was a promising drying technique for edible peanuts regarding the higher drying rate and better–quality preservation, while HAD was suitable for peanut seeds drying as it could well protect the germination rate.
